Generally, a functional layer for an organic electronic device refers to a layer that is disposed between two electrodes in an organic electronic device, such as an organic light-emitting device, an organic solar cell or an organic transistor, in order to enhance the characteristics of the device.
Materials that are currently used for this functional layer for an organic electronic device can be largely divided into inorganic materials and organic materials. The inorganic materials can further be divided into metal oxides and metal carbonates, and the organic materials can further be divided into self-assembled monolayers (SAMs), conjugated polyelectrolytes, and polyethylene oxide.
Metal oxides have a high electron mobility, a low LUMO (lowest unoccupied molecular orbital) level and a high HOMO (highest occupied molecular orbital) level, and thus are widely used as materials for functional layers for organic electronic devices. However, these metal oxides have a problem in that high-temperature processes at 200° C. or higher are required to exhibit the characteristics of the metal oxides. Such high-temperature processes have a problem in that it is difficult to realize organic electronic devices on flexible substrates, because these processes are mostly performed at temperatures higher than the glass transition temperatures of the flexible substrates. In addition, in the case in which a functional layer of metal oxide is used in an organic solar cell having an inverted structure, there is a problem in that a photoactive material is deteriorated, because the efficiency of the inverted-type organic solar cell increases to approach the efficiency of an organic solar cell having a normal structure only when it is irradiated with ultraviolet (UV) light for a predetermined time.
Meanwhile, metal carbonates and self-assembled monolayers have problems in that they have difficulties in forming uniform ultrathin films and are also difficult to be applied to continuous printing processes. In addition, although conjugated polyelectrolytes function to control the work function of electrodes by inducing an interfacial dipole on the electrode surface and thus are widely used, they have a problem in that they are considered as a major cause of increasing the costs of organic electronic devices, because a process for the synthesis thereof is complex. In addition, polyethylene oxide has a low effect of inducing an interfacial dipole, and thus the use thereof for a functional layer for an organic electronic device has a limitation.
Accordingly, there is a need for the development of novel materials other than the above-described conventional materials that are used as materials for functional layers for organic electronic devices.